United States Office of Research EPA/600/R-93/187
Environmental Protection and Development December 1993
Agency (8603)
Wildlife Exposure
Factors Handbook
Volume I of II
EPA/600/R-93/187
December 1993
WILDLIFE EXPOSURE FACTORS
HANDBOOK
Volume I of II
Office of Health and Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Washington, DC 20460
Additional major funding for this Handbook was provided by the
Office of Emergency and Remedial Response,
Office of Solid Waste and Emergency Response
and by the
Office of Science and Technology, Office of Water
U.S. Environmental Protection Agency
Washington, DC 20460
ii
DISCLAIMER
This document has been reviewed in accordance with U.S. Environmental
Protection Agency policy and approved for publication. Mention of trade names or
commercial products does not constitute endorsement or recommendation for use.
xi
FOREWORD
The Exposure Assessment Group (EAG) of EPA's Office of Research and
Development has three main functions: (1) to conduct human health and ecological
exposure and risk assessments, (2) to review exposure and risk assessments and related
documents, and (3) to develop guidelines and handbooks for use in these assessments.
The activities under each of these functions are supported by and respond to the needs of
the various program offices, regional offices, and the technical community.
The Wildlife Exposure Factors Handbook was produced in response to the
increased interest in assessing risks to ecological systems. Its purpose is to improve
exposure assessments for wildlife and support the quantification of risk estimates. It is a
companion document to the Exposure Factors Handbook, which contains information
useful for quantifying exposure to humans. Because information and methods for
estimating exposure are continually improving, we will revise these handbooks as
necessary in the future.
Michael A. Callahan
Director
Exposure Assessment Group
xii
PREFACE
The Exposure Assessment Group of the Office of Health and Environmental
Assessment (OHEA) has prepared the Wildlife Exposure Handbook in support of the Office
of Solid Waste and Emergency Response and the Office of Water. The Handbook provides
information on various factors used to assess exposure to wildlife. The goals of the
project are (1) to promote the application of risk assessment methods to wildlife species,
(2) to foster a consistent approach to wildlife exposure and risk assessments, and (3) to
increase the accessibility of the literature applicable to these assessments.
The bulk of the document summarizes literature values for exposure factors for 34
species of birds, mammals, amphibians, and reptiles. In addition, we include a chapter on
allometric equations that can be used to estimate some of the exposure factors when data
are lacking. Finally, we describe some common equations used to estimate exposure. The
basic literature search was completed in May 1990 and was supplemented by targeted
searches conducted in 1992.
We anticipate updating this Handbook and would appreciate any assistance in
identifying additional sources of information that fill data gaps or otherwise improve the
Handbook. Comments can be sent to:
Exposure Assessment Group
Wildlife Exposure Factors Handbook Project
USEPA (8603)
401 M Street, SW
Washington, DC 20460
xiii
AUTHORS, MANAGERS, CONTRIBUTORS, AND REVIEWERS
The Exposure Assessment Group (EAG) within EPA's Office of Health and
Environmental Assessment (OHEA) was responsible for preparing this document.
Additional major contract funding was provided by the Office of Emergency and Remedial
Response within the Office of Solid Waste and Emergency Response (OSWER) and by the
Office of Science and Technology within the Office of Water. The document was prepared
by ICF, Incorporated under contracts 68-C8-0003, 68-W8-0098, 68-DO-0101, and 68-C2-
0107. Susan Braen Norton served as the EAG project manager and provided overall
direction and coordination of the project. Thanks to Doug Norton for the cover illustration.
AUTHORS
Dr. Margaret McVey
Kimberly Hall, Peter Trenham, Alexander Soast, Leslie Frymier, and Ansara Hirst
ICF, Incorporated
PROJECT MANAGER
Susan Braen Norton
Exposure Assessment Group, Office of Health and Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
TASK MANAGERS
Cynthia Nolt
Office of Science and Technology
Office of Water
U.S. Environmental Protection Agency
Ron Preston
Office of Emergency and Remedial Response
Office of Solid Waste and Emergency Response
U.S. Environmental Protection Agency
CONTRIBUTORS
Dr. Sarah Gerould
Office of Water Quality
U.S. Geological Survey
xiv
Dr. Ronald Kirby
Office of Information Transfer
U.S. Fish and Wildlife Service (USFWS)
Department of the Interior
REVIEWERS
Dr. Cynthia Annett, USFWS, Arkansas Cooperative Fish and Wildlife Research
Unit, AR
Dr. Richard J. Aulerich, Michigan State University, MI
Dr. Richard Bennett, USEPA, Environmental Research Laboratory (ERL),
Corvallis, OR
Dr. Christine A. Bishop, Canadian Wildlife Service, Ontario, Canada
Dr. Brad Bortner, USFWS, Office of Migratory Bird Management, MD
Dr. Steven Bradbury, USEPA, ERL-Duluth, MN
Dr. Robert Burr, USFWS, VA
Ms. Janet Burris, ABB Environmental Services, Washington, DC
Dr. Joseph Chapman, Utah State University, UT
Dr. Lewis Cowardin, USFWS, Northern Prairie Wildlife Research Center, ND
Ms. Deanna Dawson, USFWS, Patuxent Wildlife Research Center, MD
Dr. Donald L. DeAngelis, Oak Ridge National Laboratory, TN
Dr. Bruce Duncan, USEPA, Region 10, Seattle, WA
Dr. Robert Foley, USFWS, Annapolis Field Office, MD
Dr. Glen Fox, Canadian Wildlife Service, Ontario, Canada
Dr. J.H.B. Garner, USEPA, OHEA, Environmental Criteria and Assessment Office
(ECAO), Research Triangle Park, NC
Dr. J. Whitfield Gibbons, University of Georgia, Savannah River Ecology
Laboratory, GA
Mr. Keith A. Grasman, Virginia Polytechnic Institute and State University, VA
Dr. Fred Guthery, Caesar Kleberg Wildlife Research Institute, Texas A&I
University, TX
Dr. Richard S. Halbrook, Oak Ridge National Laboratory, TN
Dr. Michael J. Hamas, Central Michigan University, MI
Dr. Charles J. Henny, USFWS, Pacific Northwest Research Station, OR
Dr. Paula F. P. Henry, USFWS, Patuxent Wildlife Research Center, MD
Dr. Gary Heinz, USFWS, Patuxent Wildlife Research Center, MD
Dr. Doug James, University of Arkansas, AR
Mr. K. Bruce Jones, USEPA, Environmental Monitoring Systems Laboratory,
EMAP Terrestrial Ecosystems, CA
Dr. Dennis G. Jorde, USFWS, Patuxent Wildlife Research Center, MD
Dr. Norm Kowal, USEPA, OHEA, ECAO, Cincinnati, OH
Dr. Gary L. Krapu, USFWS, Northern Prairie Wildlife Research Center, ND
Dr. David Krementz, USFWS, Patuxent Wildlife Research Center, MD
Dr. James Kushlan, University of Mississippi, MS
Dr. John T. Lokemoen, USFWS, Northern Prairie Wildlife Research Center, ND
Dr. Dave Ludwig, EA Engineering, Inc., MD
Dr. Drew Major, USFWS, Concord, NH
Dr. Karen McBee, Oklahoma State University, OK
xv
REVIEWERS (continued)
Dr. Linda Meyers-Schöne, International Technology Corp., NM
Mr. Jerry Moore, USEPA, OHEA, Washington, DC
Dr. Lewis Oring, University of Nevada at Reno, NV
Dr. Raymond Pierotti, University of Arkansas, AR
Dr. Richard M. Poché, Genesis Laboratories, WI
Dr. Douglas Reagan, Woodward-Clyde Consultants, CO
Dr. Lorenz Rhomberg, USEPA, OHEA, Human Health Assessment Group,
Washington, DC
Dr. Robert Ringer, Mount Dora, FL
Dr. John L. Roseberry, Southern Illinois University at Carbondale, IL
Dr. Alan Sargeant, USFWS, Northern Prairie Wildlife Research Center, ND
Dr. Edward Schafer, USDA, Denver Wildlife Research Center, CO
Dr. Laird Schutt, Canadian Wildlife Service, Quebec, Canada
Ms. Anne Sergeant, USEPA, OHEA, EAG, Washington, DC
Dr. Kim Smith, University of Arkansas, AR
Dr. Mark Sprenger, USEPA, OSWER, Environmental Response Team, Edison, NJ
Dr. George A. Swanson, USFWS, Northern Prairie Wildlife Research Center, ND
Dr. Sylvia Talmage, Oak Ridge National Laboratory, TN
Dr. Bob Trost, USFWS, Office of Migratory Bird Management, MD
Dr. D.V. (Chip) Weseloh, Canadian Wildlife Service, Ontario, Canada
Dr. Nathaniel Wheelwright, Bowdoin College, ME
Dr. Donald H. White, USFWS, Southeast Research Station, GA
Dr. Stanley N. Wiemeyer, USFWS, Patuxent Wildlife Research Center, MD
Dr. Bill Williams, Environmental Planning and Toxicology, Corvallis, OR
Dr. Dean M. Wilkinson, U.S. Department of Commerce, National Oceanic and
Atmospheric Administration, National Marine Fisheries Service
Dr. Jerry O. Wolff, USEPA, ERL, Corvallis, OR
Dr. John P. Wolfin, USFWS, Annapolis Field Station, MD
iii
CONTENTS
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii
Authors, Managers, Contributors, and Reviewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii
1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.1. PURPOSE AND SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.2. ORGANIZATION OF THE HANDBOOK . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
1.3. LIST OF SELECTED SPECIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
1.4. LIST OF EXPOSURE FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11
1.4.1. Normalizing Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11
1.4.1.1. Body Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
1.4.1.2. Growth Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
1.4.1.3. Metabolic Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
1.4.2. Contact Rate Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
1.4.2.1. Oral Route . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
1.4.2.2. Inhalation Route . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-16
1.4.2.3. Dermal Route . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-16
1.4.3. Population Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-17
1.4.3.1. Social Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-17
1.4.3.2. Home Range/Territory Size/Foraging Radius . . . . . . . . 1-17
1.4.3.3. Population Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-19
1.4.3.4. Annual Fecundity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-19
1.4.3.5. Annual Mortality and Longevity . . . . . . . . . . . . . . . . . . . 1-19
1.4.4. Seasonal Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-20
1.5. DATA PRESENTATION FORMAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-20
1.5.1. Normalizing and Contact Rate Factors . . . . . . . . . . . . . . . . . . . . . 1-21
1.5.1.1. All Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-21
1.5.1.2. Birds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-22
1.5.1.3. Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-23
1.5.1.4. Reptiles and Amphibians . . . . . . . . . . . . . . . . . . . . . . . . 1-23
CONTENTS (continued)
iv
1.5.2. Dietary Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-24
1.5.2.1. All Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-24
1.5.3. Population Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-25
1.5.3.1. All Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-25
1.5.3.2. Birds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-26
1.5.3.3. Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-27
1.5.3.4. Reptiles and Amphibians . . . . . . . . . . . . . . . . . . . . . . . . 1-27
1.5.4. Seasonal Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-28
1.5.4.1. Birds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-29
1.5.4.2. Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-29
1.5.4.3. Reptiles and Amphibians . . . . . . . . . . . . . . . . . . . . . . . . 1-29
1.5.5. Abbreviations Used in Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-29
1.6. LITERATURE SEARCH STRATEGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-30
1.7. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-32
viii
LIST OF TABLES
Table 1-1. Characteristics of Selected Birds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8
Table 1-2. Characteristics of Selected Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9
Table 1-3. Characteristics of Selected Reptiles and Amphibians . . . . . . . . . . . . . . . 1-10
Table 1-4. Wildlife Exposure Factors Included in the Handbook . . . . . . . . . . . . . . . . 1-12
Table 1-5. Wildlife Contact Rate Exposure Factors . . . . . . . . . . . . . . . . . . . . . . . . . . 1-15
Table 1-6. Column Headers for Tables of Normalizing and Contact
Rate Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-21
Table 1-7. Column Headers for Tables on Dietary Composition . . . . . . . . . . . . . . . . 1-24
Table 1-8. Column Headers for Tables of Factors for Population Dynamics . . . . . . 1-26
Table 1-9. Column Headers for Tables on Seasonal Activities . . . . . . . . . . . . . . . . . 1-28
1-1
1. INTRODUCTION
The Wildlife Exposure Factors Handbook (hereafter referred to as the Handbook)
provides data, references, and guidance for conducting exposure assessments for wildlife
species exposed to toxic chemicals in their environment. It is the product of a joint effort
by EPA's Office of Research and Development (ORD), Office of Solid Waste and
Emergency Response (OSWER), and Office of Water (OW). The goals of this Handbook are
(1) to promote the application of risk assessment methods to wildlife species, (2) to foster
a consistent approach to wildlife exposure and risk assessments, and (3) to increase the
accessibility of the literature applicable to these assessments.
1.1. PURPOSE AND SCOPE
The purpose of the Handbook is to provide a convenient source of information and
an analytic framework for screening-level risk assessments for common wildlife species.
These screening-level risk assessments may be used for several purposes, including: to
assess potential effects of environmental contamination on wildlife species and to support
site-specific decisions (e.g., for hazardous waste sites); to support the development of
water-quality or other media-specific criteria for limiting environmental levels of toxic
substances to protect wildlife species; or to focus research and monitoring efforts. The
Handbook provides data (analogous to EPA's Exposure Factors Handbook for humans,
USEPA, 1989c) and methods for estimating wildlife intakes or doses of environmental
contaminants. Although the data presented in the Handbook can be used for screening
analyses, we recommend that anyone establishing a cleanup goal or criterion on the basis
of values contained herein obtain the original literature on which the values are based to
confirm that the study quality is sufficient to support the criterion. This Handbook does
not include data or extrapolation methods required to assess the toxicity of substances to
wildlife species, nor does it include any chemical-specific data (e.g., bioavailability factors).
For the Office of Water, data gathered for the Handbook were used to identify
wildlife species that are likely to be at greater risk from bioaccumulative pollutants in
surface waters and to estimate likely exposures for these species. Data on diets and on
1-2
food and water ingestion rates can be used with chemical-specific information, such as
bioaccumulation potential and wildlife toxicity, to calculate site- or region-specific
concentrations of a chemical in water (or soil or sediment) that are unlikely to cause
adverse effects.
For the Superfund program, this Handbook supplements the existing environmental
evaluation guidance. EPA's Risk Assessment Guidance for Superfund: Volume II--
Environmental Evaluation Manual (U.S. EPA, 1989a) provides an overview of ecological
assessment in the Superfund process. It includes a description of the statutory and
regulatory bases for ecological assessments in Superfund and fundamental concepts for
understanding ecological effects of environmental contaminants. The Environmental
Evaluation Manual also reviews elements of planning an ecological assessment and how to
organize and present the results of the assessment. EPA's Ecological Assessment of
Hazardous Waste Sites: A Field and Laboratory Reference (U.S. EPA, 1989b) and
Evaluation of Terrestrial Indicators for Use in Ecological Assessments at Hazardous Waste
Sites (U.S. EPA, 1992) are companion documents that describe biological assessment
strategies, field sampling designs, toxicity tests, biomarkers, biological field assessments,
and data interpretation. The ECO Update intermittent bulletin series (published by EPA's
Office of Solid Waste and Emergency Response, publication no. 9345.0-05I, available from
the National Technical Information Service, Springfield, Virginia) provides supplemental
guidance for Superfund on selected issues. Although these documents have identified
decreases in wildlife populations as potential endpoints for ecological assessments, they
do not provide guidance on how to conduct a wildlife exposure assessment that is
comparable to the guidance provided by the Superfund program for human health
exposure assessments. This Handbook provides both guidance and data to facilitate
estimating wildlife exposure to contaminants in the environment.
Exposure assessments for wildlife and humans differ in several important ways.
One key distinction is that many different wildlife species may be exposed, as compared
with a single species of concern for a human health assessment. Exposure varies between
different species and even between different populations of the same species; behavioral
attributes and diet and habitat preferences influence this variation. Second, whereas it is
1-3
seldom possible to confirm estimated levels of human exposure without invasive sampling
of human tissues, confirmatory sampling for many chemicals can be done in wildlife
species (protected species excepted). However, the tissue sampling required to quantify
actual exposure levels can be costly, and interpretation of tissue concentrations can be
complex.
For both human health and wildlife exposure assessments, the most cost-effective
approach is often to first screen for potentially significant exposures using measures (or
estimates) of environmental contamination (e.g., in soils, water, prey species) to estimate
contaminant intakes or doses by significant routes of exposure. If estimated doses fall far
below the toxicity values associated with adverse effects, especially from chronic
exposures, further assessment may be unnecessary. If estimated doses far exceed
reference toxicity values, it may be possible to determine appropriate actions on the basis
of these estimates alone. When a screening-level exposure assessment indicates that
adverse effects are likely, additional confirmatory data may be needed in the decisionmaking
process. For humans, it is usually not practicable to obtain additional types of data
(e.g., tissue concentrations, biomarkers), and human exposure estimates are often refined
by using more site-specific data for exposure parameters. For wildlife, confirmatory data
may be obtained from chemical analyses of tissue samples from potentially exposed
wildlife or their prey and from observed incidence of disease, reproductive failure, or death
in exposed wildlife. These are reviewed in EPA's field and laboratory reference and
terrestrial indicators documents described above (EPA, 1989b, 1992). If this more direct
approach is not possible, the exposure analysis can be refined on the basis of more sitespecific
data for the species of concern.
Wildlife can be exposed to environmental contaminants through inhalation, dermal
contact with contaminated water or soil, or ingestion of contaminated food, water, or soil.
Exposure assessment seeks to answer several questions, including:
 What organisms are actually or potentially exposed to contaminants?
1-4
 Which organisms or life stages might be most vulnerable to environmental
contaminants (e.g., ingest the largest quantities of contaminated media
relative to body size)?
 What are the significant routes of exposure?
 To what amounts of each contaminant are organisms actually or potentially
exposed?
 How long is each exposure?
 How often does or will exposure to the environmental contaminants take
place?
 What seasonal and climatic variations in conditions are likely to affect
exposure?
 What are the site-specific geophysical, physical, and chemical conditions
affecting exposure?
The parameters for which data are presented in the Handbook are intended to help a risk
assessor answer these questions. The population parameter data (e.g., birth and death
rates) may be useful for placing estimates of risks to wildlife populations in a broader
ecological context and for planning monitoring activities.
This Handbook focuses on selected groups of mammals, birds, amphibians, and
reptiles. Fish and aquatic or terrestrial invertebrates were not included in this effort. The
profiles on amphibians and reptiles are, in general, less developed than those for birds and
mammals. We emphasized birds and mammals because methods for assessing their
exposure are more common and well developed. As more assessments are done for
amphibians and reptiles, we anticipate that additional methods and supporting factors will
be necessary. Until then, we hope the information presented here will encourage
assessors to begin considering and quantifying their exposure.
For all exposure parameters and species in the Handbook, we try to present data
indicative of the range of values that different populations of a species may assume across
North America. For site-specific ecological risk assessments, it is important to note that
the values for exposure factors presented in this Handbook may not accurately represent
1-5
specific local populations. The species included in the Handbook have broad geographic
ranges, and they may exhibit different values for many of the exposure factors in different
portions of their range. Some species exhibit geographic variation in body size, survival,
and reproduction. Breeding and migration also influence exposure. Site-specific values
for these parameters can be determined more accurately using published studies of local
populations and assistance from the U.S. Fish and Wildlife Service, state departments of
fish and game, and organizations such as local Audubon Society chapters. In addition, The
Nature Conservancy develops and maintains wildlife databases (including endangered
species) in cooperation with all 50 states. Local information increases the certainty of a
risk assessment. Thus, for site-specific assessments, we strongly recommend contacting
local wildlife experts to determine the presence and characteristics of species of concern.
Finally, we do not intend to imply that risk assessments for wildlife should be
restricted to the species described in this Handbook, or should always be conducted for
these species. We emphasize that locally important or rare species not included in this
Handbook may still be very important for site-specific risk assessments. To assist users
who wish to evaluate other species, we list general references for birds, mammals,
reptiles, and amphibians in North America. The Handbook also provides allometric
equations to assist in extrapolating exposure factors (e.g., water ingestion rate, surface
area) to closely related species on the basis of body size.
1.2. ORGANIZATION OF THE HANDBOOK
The Handbook is organized into four chapters. The remainder of this chapter
provides an overview of the species and exposure factors included in the Handbook and
discusses the literature search strategy used to identify factors. Chapter 2 presents
exposure profiles for the selected species (described in greater detail below). Chapter 3
provides allometric models that may be used to estimate food and water ingestion rates,
inhalation rates, surface areas, and metabolic rates for wildlife species on the basis of
body size. Chapter 4 describes common equations used to estimate wildlife exposure to
environmental contaminants. Included are methods for estimating diet-specific food
1-6
ingestion rates on the basis of metabolic rate and for estimating exposure to chemicals in
soil and sediment.
Chapter 2 is the core of the Handbook; it presents exposure profiles for selected
birds (Section 2.1), mammals (Section 2.2), and reptiles and amphibians (Section 2.3),
along with brief descriptions of their natural history. Each species profile includes an
introduction to the species' general taxonomic group, qualitative description of the
species, list of similar species, table of exposure factors, and reference list (which also
covers that species' section in Volume II, the Appendix). The values included in the
exposure factors tables are a subset of those we found in the literature and also include
values that we estimated using the allometric equations presented in Chapter 3. We
selected values for the tables in Chapter 2 based on a variety of factors including sample
size, quantification of variability (e.g., standard deviations, standard errors, ranges),
relevance of the measurement technique for exposure assessment, and coverage of
habitats, subspecies, and the variability seen in the literature. A complete listing of the
parameter values identified in our literature survey is provided in the Appendix. The
Appendix also includes more details concerning sample size, methods, and qualifying
information than the species profiles. Users are encouraged to consult the Appendix to
select the most appropriate values for their particular assessment.
The remainder of this introductory chapter describes the species and exposure
factors covered in the Handbook in greater detail. The literature search strategy is
discussed in Section 1.6.
1.3. LIST OF SELECTED SPECIES
Wildlife species were selected for the Handbook to provide several types of
coverage:
 Major taxonomic groups (major vertebrate groups, orders, and families);
 A range of diets (e.g., piscivore, probing insectivore) likely to result in
contact with contaminated environmental media;
1-8
Table 1-1. Characteristics of Selected Birds
Diet General Foraging Habitat Body Size Selected Bird Species
Insectivorea
probing/soil-dwelling invertebrates woodlands, marshes medium American woodcock
gleaning/insects marshes small marsh wren
Herbivore
gleaning/seeds woodlands, fields and brush medium northern bobwhite
grazing/shoots open fields large Canada goose
Omnivore open woodland, suburbs small American robin
Carnivore open fields, forest edge medium American kestrelb
most open areas medium red-tailed hawk
Carnivore/Piscivore/Scavenger
small birds & mammals/fish/dead fish open water bodies large bald eagle
fish/invertebrates/small birds/garbage Great Lakes and coastal medium herring gull
Piscivore most streams, rivers, small medium belted kingfisherc
lakes
most freshwater and saltwater large great blue heron
bodies
large water bodies large osprey
Aquatic Insectivored
probing/soil-dwelling invertebrates most rivers and streams small spotted sandpiper
diving/aquatic invertebrates oceans and coastal areas medium lesser scaup
Aquatic Herbivore/Insectivore most wetlands, ponds medium mallard
Includes consumption of insects, other arthropods, worms, and other terrestrial invertebrates.a
Includes consumption of terrestrial vertebrates and large invertebrates.b
Includes consumption of fish, amphibians, crustaceans, and other larger aquatic animals.c
Includes consumption of aquatic invertebrates and amphibian larvae by gleaning or probing.d
1-9
Table 1-2. Characteristics of Selected Mammals
Diet General Foraging Habitat Body Size Mammal Species
Selected
Insectivorea
gleaning/surface-dwelling invertebrates most habitat types small short-tailed shrew
Herbivore
gleaning/seeds most dry-land habitats small deer mouse
grazing or browsing/shoots, roots, or grassy fields, marshes, bogs small meadow vole
leaves prairie grass communities small prairie vole
most habitat types medium eastern cottontail
Omnivore woodlands, suburbs medium raccoon
mixed woodlands and open medium red fox
areas
Carnivore most areas near water medium minkb
Piscivore rivers medium river otterc
coastal, estuaries, lakes medium harbor seal
Aquatic Herbivore most aquatic habitats medium muskrat
Includes consumption of insects, other arthropods, worms, and other terrestrial invertebrates.a
Includes consumption of aquatic and terrestrial vertebrates and large invertebrates.b
Includes consumption of fish, amphibians, crustaceans, molluscs, and other large aquatic animals.c
1-10
Table 1-3. Characteristics of Selected Reptiles and Amphibians
Adult Diet for Adults Body Size Amphibian Species
General Foraging Habitat Selected Reptile or
REPTILES
Terrestrial Carnivore open woods, fields and brush medium racera
Aquatic Piscivore most types of water bodies medium northern water snakeb
Omnivore open fields, forest edge, medium eastern box turtle
marshes
most freshwater bodies large snapping turtle
Aquatic Herbivore most wetlands, ponds medium painted turtle
AMPHIBIANS
Insectivore shallow freshwater bodies small green frogc
Aquatic Piscivore/Insectivore lakes, ponds, bogs, streams medium bullfrogd
small lakes, ponds, streams small eastern newt
Includes consumption of terrestrial vertebrates and invertebrates, insects, other arthropods, worms, and other terrestrial invertebrates.a
Includes consumption of fish, amphibians, and crustaceans.b
Includes consumption of insects, other arthropods, worms, and other terrestrial invertebrates.c
Includes consumption of fish, amphibians, crustaceans, molluscs, other aquatic animals, and terrestrial insects and other invertebrates.d
1-11
 Species of societal significance or concern (e.g., game species, familiar
species); and
 Species that have been shown to be particularly sensitive to the stressor
being addressed.
When species of concern for a risk assessment include species for which data are
presented in this Handbook, it can serve as a readily available source of data for
screening-level exposure analyses.
1.4. LIST OF EXPOSURE FACTORS
Three routes of exposure may be of concern for wildlife in the vicinity of
contaminated surface waters and terrestrial habitats: oral, inhalation, and dermal. Oral
exposures might occur via ingestion of contaminated food (e.g., aquatic prey) or water or
incidental ingestion of contaminated media (e.g., soils, sediments) during foraging or other
activities. Inhalation of gases or particulates might be a significant route of exposure for
some animals. Dermal exposures are likely to be most significant for burrowing mammals
(i.e., via contact with contaminated soils) and animals that spend considerable amounts of
time submerged in surface waters. This Handbook tabulates selected data for all three
routes of exposure (Table 1-4), emphasizing oral exposures. It also provides quantitative
information on population parameters and qualitative information related to seasonal
activities, geographic ranges, habitats, and other life-history characteristics.
The exposure factors presented in the Handbook are conceptually separated into
four types: normalizing factors (Section 1.4.1), contact rates (Section 1.4.2), population
dynamics (Section 1.4.3), and seasonal activities (Section 1.4.4). Section 1.5 describes the
format in which values for these exposure factors are presented in Chapter 2.
1.4.1. Normalizing Factors
Normalizing factors include body weight, growth rate, and metabolic rate, which are
discussed in turn below.
1-13
1.4.1.1. Body Weight
Body weights (in units of mass) are reported as fresh weight as might be obtained
by weighing a live animal in the field. Several of the contact rate parameters are
normalized to body weight. For example, both food and water ingestion rates are reported
on a per body weight basis (e.g., gram of fresh food or water per gram of fresh body weight
per day). Using empirical models, body weight data also were used to estimate contact
rate parameters for which we could not find measured values.
Adult body weights are listed for all species. For birds, we also provide egg weight,
weight at hatching, nestling or chick weights, and weight at fledging, when available, to
assist risk assessors concerned with estimating exposures of embryos and young birds.
For mammals, we also provide gestating female weight, birth weight, pup weights at
various ages, weight at weaning, and weight at sexual maturity, when available, for a
similar purpose. Finally, for reptiles and amphibians, we also provide egg weight, larval or
juvenile weights with age, and weight at metamorphosis, if available and applicable. Body
size for reptiles and amphibians is often reported as body length instead of body weight,
so we also provide data on body length and the relationship between body length and body
weight, when available.
1.4.1.2. Growth Rate
Young animals generally consume more food (per unit body weight) than adults
because they grow and develop rapidly. Growth rates change as animals mature, whether
expressed as absolute (g/day) or relative (percent body weight) terms. Weight gain is rapid
after birth, but slows over time. Different types of animals exhibit different patterns of
growth over time. Plots of body weight versus age for some animal groups are sigmoidal
whereas others may approximate logistic functions or other shapes. As a result,
investigators often report growth rates as various constants associated with particular
mathematical models (e.g., Gompertz equation, von Bertalanffy equation; see Peters, 1983)
that fit the growth pattern for a given species. Instead of presenting a variety of growth
constants and models, however, we report growth rates for young animals, when available,
1-14
in grams per day for specific age groups. Growth rates also can be inferred from a series
of juvenile body weights with age. These measures are included under body weight (see
Section 1.4.1.1).
1.4.1.3. Metabolic Rate
Metabolic rate is reported on the basis of kilocalories per day normalized to body
weight (e.g., kcal/kg-day). If metabolic rate was measured and reported on the basis of
oxygen consumption only, we provide those values as liters O /kg-day. Normalized2
metabolic rates based on kilocalories can be used to estimate normalized food ingestion
rates (see Section 4.1.2). Metabolic rates based on oxygen consumption can be used to
estimate metabolic rates based on kilocalories for subsequent use in estimating food
ingestion rates (see Section 3.6.3.1).
1.4.2. Contact Rate Factors
Table 1-5 summarizes the six contact rate factors included for the oral, inhalation,
and dermal routes of exposure.
1.4.2.1. Oral Route
Three environmental media are the primary contributors to wildlife exposure by the
oral route: food, water, and soils and sediments. Four contact rate exposure parameters
related to these three exposure media are discussed below.
1.4.2.1.1. Food ingestion rates. Food ingestion rates are expressed in this
Handbook as grams of food (wet weight) per gram of body weight (wet weight) per day
(g/g-day). Food ingestion rates can vary by age, size, and sex and by seasonal changes in
ambient temperature, activity levels, reproductive activities, and the type of diet consumed.
Food ingestion rates have not been measured for many wildlife species. Methods for
estimating food ingestion rates on the basis of free-living (or field) metabolic rate, energy
content of the diet, and assimilation efficiency are discussed in Section 4.1.2.
1-15
Table 1-5. Wildlife Contact Rate Exposure Factors
Exposure
Route Medium Factor Expression Units
ORAL Food ingestion rate fraction body
weight
6 g/g-day
dietary
composition
fraction of total
intake
represented by
each food type
Water ingestion rate fraction body
weight
g/g-day
Soil/Sediment intake rate fraction of total
food intake
g/g-day
INHALATION Vapor or
Particulates
inhalation rate daily volume m /day3
DERMAL Water or
Soil/Sediment
surface area total area
potentially
exposeda
cm2
Total unprotected or permeable surface area that might be exposed under some circumstances (e.g., dusta
bathing), even though it would not be exposed under other conditions (e.g., swimming with a trapped air
layer between the feathers or fur and skin).
1.4.2.1.2. Dietary composition. Dietary composition varies seasonally and by age,
size, reproductive status, and habitat. Dietary composition (e.g., proportion of diet
consisting of various plant or animal materials), often measured by stomach-content
analyses, is expressed whenever possible as percentage of total intake on a wet-weight
basis. This convention facilitates comparison with contaminant concentrations in dietary
items reported on a wet-weight basis. Methods for converting other measures of dietary
composition (e.g., percentage of total prey items captured, proportion of intake on a dryweight
basis) to estimates of dietary intake on a wet-weight basis are provided in Section
4.1.2.
1.4.2.1.3. Water ingestion rates. For drinking-water exposures, ingestion rates are
expressed in this Handbook as grams of water per gram of wet body weight per day (g/gday).
Water consumption rates depend on body weight, physiological adaptations,
1-16
diet, temperature, and activity levels. It is important to remember that, under some
conditions, some species can meet their water requirements with only the water contained
in the diet and metabolic water production (see Section 3.2).
1.4.2.1.4. Incidental soil and sediment intakes. Wildlife can incidentally ingest
soils or sediments while foraging or during other activities such as dust bathing and
preening or grooming. Data quantifying soil and sediment ingestion are limited; we
present available values for selected species in Section 4.1.3.
1.4.2.2. Inhalation Route
Average daily inhalation rates are reported in the Handbook in units of m /day.3
Inhalation rates vary with size, seasonal activity levels, ambient temperature, and daily
activities. EPA's current approach to calculating inhalation exposures requires additional
information on species' respiratory physiology to fully estimate inhalation exposures (see
Section 4.1.4).
1.4.2.3. Dermal Route
Dermal contact with contaminated soil, sediment, or water is likely to be an
exposure pathway for some wildlife species. An animal's surface area could be used to
estimate the potential for uptake of contaminants through its skin. For some exposures
(e.g., dust bathing), the entire surface area of the animal might be important. For other
types (e.g., swimming), only the uninsulated portions (e.g., no fur or feathers that create a
trapped air layer) of the animal might contact the contaminated medium. In the Handbook,
we provide measures or estimates of the entire potentially exposed surface area of an
animal, when possible. We have not attempted to determine what portions would be
exposed and protected for swimming animals.
1-17
1.4.3. Population Dynamics
Several parameters can be used to describe the spatial distribution and abundance
of a population of animals in relation to the spatial extent of contamination. Three
parameters related to spatial distribution are social organization, home-range size, and
population density. These are important for estimating the number of individuals or
proportion of a population that might be exposed to a contaminated area. Parameters
related to population size and persistence include age at sexual maturity and maturation,
mortality, and annual fecundity rates. These parameters may be useful to assessors
planning or evaluating field studies or monitoring programs.
1.4.3.1. Social Organization
The Handbook includes a qualitative description of each species' social
organization, which influences how animals of various ages and sizes are distributed in
space. In some species, individual home ranges do not overlap. In others, all individuals
use the same home range. In between these extremes, home ranges can be shared with
mates, offspring, or extended family groups.
Social organization can vary substantially among species that appear otherwise
similar; therefore, it is not possible to extrapolate the social organization of similar species
from the selected species in this Handbook. Consult the general bibliographies for
information sources to determine the social organization of species not covered in the
Handbook.
1.4.3.2. Home Range/Territory Size/Foraging Radius
Home range size can be used to determine the proportion of time that an individual
animal is expected to contact contaminated environmental media. Home range is defined
as the geographic area encompassed by an animal's activities (except migration) over a
specified time. While home range values often are expressed in units of area, for species
dependent on riparian or coastal habitats, a more meaningful measure can be foraging
1-18
radius, or the distances the animals are willing to travel to potential food sources. Although
home ranges may be roughly circular in homogeneous habitats, it is important to
remember that depending on habitat needs and conditions, home ranges may be irregular
in shape. The size and spatial attributes of a home range often are defined by foraging
activities, but also might depend on the location of specific resources such as dens or nest
sites in other areas. An animal might not visit all areas of its home range every day or
even every week, but over longer time periods, it can be expected to visit most of the areas
within the home range that contain needed resources such as forage, prey, or protected
resting areas.
Home range size for individuals within a population can vary with season, latitude,
or altitude as a consequence of changes in the distribution and abundance of food or other
resources. It generally varies with animal body size and age because of differences in the
distribution of preferred forage or prey. It can also depend on habitat quality, increasing as
habitat quality decreases to a condition beyond which the habitat does not sustain even
sparse populations. Finally, home ranges can vary by sex and season. For example, if a
female is responsible for most or all of the feeding of young, her foraging range might be
restricted to an area close to her nest or den when she has dependent young, whereas the
foraging range of males would not be so restricted.
Nonterritorial species may allow significant overlap of activity areas among
neighboring individuals or groups. For example, several individuals or mated pairs may
share the same area, although signalling behaviors may ensure temporal segregation. For
these species, we report a home range size or foraging radius. Other species are strongly
territorial and defend mutually exclusive areas: individuals, breeding pairs, or family units
actively advertise identifiable boundaries and exclude neighboring individuals or groups.
Foraging activities are usually restricted to the defended territories. For these species, we
report the size of the defended territory and note whether foraging occurs outside of the
territory.
1-19
1.4.3.3. Population Density
Population density (the number of animals per unit area) influences how many
individuals (or what proportion of a local population) might be exposed within a
contaminated area. For strongly territorial species, population density can be inferred
from territory size in many cases. For species with overlapping home ranges, particularly
colonially breeding animals (e.g., most seabirds), population density cannot be inferred
from home range size.
1.4.3.4. Annual Fecundity
Attributes related to the number of offspring produced each year that reach sexual
maturity (annual fecundity) are measured in different ways depending on the life history of
the species. For birds, data are generally available for clutch size, number of clutches per
year, nest success (generally reflecting predation pressure), number of young fledged per
successful nest (generally reflecting food availability), and number of young fledged per
active nest (reflecting all causes of mortality). For mammals, litter size in wild populations
often is determined by placental scars or embryo counts, and the number of young
surviving to weaning is seldom known. For reptiles that lay eggs, clutch size and percent
hatching can be measured in the field. For viviparous reptiles, we report the number born
in a litter. For amphibians, egg masses may include thousands of eggs, but these are
seldom counted.
1.4.3.5. Annual Mortality and Longevity
Longevity can influence the potential for cumulative deleterious effects and the
appropriate averaging times for chronic exposures. For birds, annual adult mortality tends
to be constant. For large mammalian species, however, annual adult mortality tends to be
constant for several years, and then increases rapidly with age. For reptiles and
amphibians, annual adult mortality can decrease with age for some time as the animals
continue to grow larger and become less susceptible to predation. In the Handbook, we
1-20
report annual mortality rates by age category and typical or mean and maximum
longevities, when possible.
1.4.4. Seasonal Activities
Many life-cycle attributes affect an animal's activity and foraging patterns in time
and space. For example, many species of birds are present in the northern hemisphere
only during the warmer months or move seasonally between the northern and southern
parts of North America. Some species of mammals, reptiles, and amphibians hibernate or
spend a dormant period in a burrow or den during the winter months. The species profiles
describe these and other seasonal activity patterns that can influence exposure frequency
and duration.
For each species, we summarize information on the seasonal occurrence of several
activities including breeding, molting, migration, dispersal, and occurrence of
dormancy/denning (if applicable). Deposition and utilization of fat reserves are discussed
where information is available. Trends in these factors with latitude are identified.
1.5. DATA PRESENTATION FORMAT
Species-specific values for the exposure factors are presented in Chapter 2.
Quantitative data for each species are presented in tables arranged in four main sections:
 Normalizing and Contact Rate Factors;
 Dietary Composition;
 Population Dynamics; and
 Seasonal Activities.
The parameter values and units used for each exposure factor are described in the
remainder of this section. In the species profiles and in the Appendix, all values are
identified as measured or estimated, and references are provided.
1-21
Age/Sex/ Age (e.g., A for adult, J for juvenile)
Cond./Seas. Sex (e.g., M for male, F for female)
Condition (e.g., I for incubating, NB for nonbreeding)
Season (e.g., SP for spring, SU for summer).
[Note: Only information needed to correctly interpret the value is
included.]
Mean Mean value for population sampled ± standard deviation (SD), if
reported. If SD is not reported, mean value for population sampled ±
standard error (SE) of the mean, if reported. For some studies, a
range of typical values may be presented instead of a mean value
(check the notes).
Range or Range of values reported for the population sampled, or
(95% CI of (95th percent confidence interval of the mean value).
Mean)
Location State(s) or province(s) in which the study was conducted
(subspecies) (subspecies studied, if reported).
Reference Reference for study.
Note No. Footnote number.
Table 1-6. Column Headers for Tables of Normalizing and Contact Rate Factors
1.5.1. Normalizing and Contact Rate Factors
Normalizing and contact rate factors are presented under the heading "Factors" in
Chapter 2. Several of them apply to all animals included in the Handbook, whereas some
apply only to specific groups, as described in Sections 1.5.1.1 through 1.5.1.4. The column
headers for these factors are explained in Table 1-6.
1.5.1.1. All Animals
Body weight (grams or Measured values only. Although we use the term
kilograms) weight, all data are presented in units of mass. The age
and sex of the animal are specified as appropriate, and
1-22
weights may include age-weight series for young
animals.
Metabolic rate (liters O /kg-day) Included only if measured values were available. These2
data can be used to estimate metabolic rate on a kcal
basis.
Metabolic rate (kcal/kg-day) Measured or estimated basal and free-living (or field)
metabolic rates. Most of the free-living values were
estimated from body weight using an appropriate
allometric equation.
Food ingestion rate (g/g-day) Measured on a wet-weight basis. For birds and
mammals, values measured in captivity are generally
lower than for free-ranging animals. For reptiles and
amphibians, food ingestion rates can be higher in
captivity than in the field. Food ingestion rates can also
be different in captivity than in the wild if the diet differs
substantially from that consumed in the wild (e.g., dry
laboratory chow has a substantially lower water content
than most natural diets).
Water ingestion rate (g/g-day) Most of these values were estimated from body weight
using an allometric equation.
Sediment/soil ingestion rate These values are not presented in the individual species
profiles in Chapter 2; instead, the limited data available
for soil/sediment ingestion rates (as percent soil or
sediment in diet on a dry weight basis) for selected
species are presented in Section 4.1.3.
Inhalation rate (m /day) Note that this value is not normalized to body weight,3
but is the total volume inhaled each day. Most values
were estimated from body weight using an appropriate
allometric equation.
Surface area (cm ) Most values were estimated from body weight using an2
appropriate allometric equation.
1.5.1.2. Birds
Egg weight (grams) Included only if measured values were available.
Weight at hatching (grams) Included only if measured values were available.
1-23
Chick or nestling growth Included only if measured values were available. The
rate (g/day) ages to which the growth rate applies are indicated.
Weight at fledging (grams) Included only if measured values were available.
1.5.1.3. Mammals
Neonate weight (grams) Included only if measured values were available.
Pup growth rate (g/day) Included only if measured values were available. The
ages to which the growth rate applies are indicated.
Weight at weaning (grams) Included only if measured values were available.
1.5.1.4. Reptiles and Amphibians
Body length (mm) Length is the most common measure of size and growth
rate reported for reptiles and amphibians. Body lengthweight
relationships are reported whenever possible.
Data for snakes include snout-to-vent lengths (SVL) and
total lengths; for frogs, SVLs only; and for turtles,
carapace (dorsal shell) and plastron (ventral shell)
lengths.
Egg weight (grams) Included only if measured values were available.
Weight at hatching (grams) Included only if measured values were available.
Juvenile growth rate (g/day) Included only if measured values were available. The
ages to which the growth rate applies are indicated.
Tadpole weight (grams) For frogs only; included only if measured values were
available.
Larval or eft weight (grams) For newts only; included only if measured values were
available.
1-24
Dietary Composition List of food types.
Spring Dietary composition during spring (March, April, May).
Summer Dietary composition during summer (June, July, August).
Fall Dietary composition during fall (September, October,
November).
Winter Dietary composition during winter (December, January,
February).
Location State(s) or Canadian province(s) in which study was
(subspecies)/ conducted (subspecies studied, if reported).
Habitat Type of habitat associated with the reported values
(measure) (measure used to quantify dietary composition).
Reference Reference for study.
Note No. Footnote number.
Table 1-7. Column Headers for Tables on Dietary Composition
1.5.2. Dietary Composition
1.5.2.1. All Animals
The diet of all animals is separated by season whenever possible. Up to three
months of data were combined for each of the four seasons, provided the animals were in
the same location and habitat during the 3-month period (Table 1-7). The diet components
are listed in the first column shaded in grey. The measure of dietary composition is
enclosed in parentheses under the "Location (subspecies)/Habitat (measure)" column
header.
Dietary composition can be expressed in many ways. In the Appendix, we have
presented all measures of dietary composition encountered in the literature review. In the
species profiles in Chapter 2, we have emphasized dietary composition measured as the
percentage of the total food intake of each food type on a wet-weight basis. These data
1-25
are usually determined by analysis of stomach or other digestive tract contents. For
entries based on these measures, the total of the values listed under each seasonal
column should approximate 100 percent. As Chapter 4 indicates, it is relatively simple to
estimate contaminant intakes when dietary composition is measured on a wet-weight
basis. Dietary composition may also be measured on a dry-weight basis; information on
the relative water content of the different dietary items provided in Chapter 4 can be used
to convert dry-weight composition to wet-weight composition if needed. Dietary
composition is often reported as frequency of occurrence in digestive tract contents,
scats, or regurgitated pellets. For these measures, the total of the values in the seasonal
columns can exceed 100 (e.g., fish occurred in 90 percent of scats, amphibia in 75 percent
of scats, and molluscs in 15 percent of scats). We do not provide guidance on how to
estimate contaminant intakes based on these measures; however, studies using these
measures can indicate seasonal and geographic differences in diet.
1.5.3. Population Dynamics
Distribution and mortality parameters can be defined similarly for birds, mammals,
reptiles, and amphibians (Section 1.5.3.1). Reproductive parameters, however, differ
among these groups (Sections 1.5.3.2 through 1.5.3.5). The column headers for population
dynamics are described in Table 1-8.
1.5.3.1. All Animals
Home range size (ha)/ Area usually listed in hectares, radius in kilometers. The home
Territory size (ha)/ range for species such as mink or kingfishers, which spend
Foraging radius (m) most of their time along shoreline areas, is sometimes
described as kilometers of shoreline. For some species with
extremely small breeding territories, we used m instead of2
hectares. For colonially nesting birds, foraging radii are listed
in kilometers. For frogs, we found information only on male
breeding territory size, which does not include the foraging
range of either sex.
Population density Usually listed as number (N) of individuals per hectare,
(N/ha) although numbers of breeding pairs or nests per hectare are
used for some species.
1-26
Age/Sex/ Age (e.g., A for adult, J for juvenile)
Cond./Seas. Sex (e.g., M for male, F for female)
Condition (e.g., I for incubating, NB for nonbreeding)
Season (e.g., SP for spring, SU for summer).
[Note: Only information needed to correctly interpret the value is
included.]
Mean Mean value for population sampled ± standard deviation (SD), if
reported. If SD is not reported, mean value for population sampled ±
standard error (SE) of the mean, if reported. For some studies, a
range of typical values may be presented instead of a mean.
Range Range of values reported for the population sampled.
Location State(s) or province(s) in which the study was conducted
(subspecies)/ (subspecies studied, if reported).
Habitat Type of habitat associated with the reported values.
Reference Reference for study.
Note No. Footnote number.
Table 1-8. Column Headers for Tables of Factors for Population Dynamics
Age at sexual maturity Age at which first successful reproduction occurs. In many
long-lived species, only a portion of the population breeds at
this age.
Annual mortality rates Usually listed as percent per year. Can vary with age and sex
of the animal.
Longevity Mean longevity of adult members of the population (does not
include juvenile mortality). When available, an estimate of
maximum longevity is also provided (usually from studies of
captive individuals).
1.5.3.2. Birds
Clutch size Number of eggs laid per active nest (usually the number laid
per female, but in some species, more than one female may lay
in a single nest).
1-27
Clutches per year Number of successful clutches laid per year. Additional
clutches may be laid if a clutch is lost early in incubation.
Days incubation Measured from day incubation starts (often after laying of last
egg) to hatching.
Age at fledging Age at which young can maintain sustained flight. Parents
usually continue to feed or to accompany young for some time
after fledging.
Number fledged per Number fledged for each nest for which incubation was
active nest initiated.
Percent nests Percent of active nests hatching eggs.
successful
Number fledged per Number fledged for each nest for which at least one young
successful nest hatched.
1.5.3.3. Mammals
Litter size Based on embryo counts whenever possible. Use of placental
scars can result in overestimation of litter size and counts of
live pups in dens can result in underestimation of litter size.
Litters per year Number of litters born each year.
Days gestation Days of active gestation. For species with delayed
implantation, this period can be substantially shorter than the
period from mating to birth.
Pup growth rate Usually reported as grams per day during a specified age
interval. May be reported instead as a series of weights for
pups of specified ages.
Age at weaning Age when the pups begin to leave the nest or den to actively
feed for most of their food.
1.5.3.4. Reptiles and Amphibians
Clutch or litter size Number of eggs laid per female for egg-laying species; number
of live offspring born for species bearing live young (e.g., water
snake). Reported by age and size of the female when
appropriate.
1-28
Begin Month that the activity usually begins.
Peak Month(s) that the activity peaks (most of the population is involved).
End Month that the activity usually ends.
Location State(s) or province(s) in which the study was conducted
(subspecies) (subspecies studied, if reported).
Reference Reference for study.
Note No. Footnote number.
Table 1-9. Column Headers for Tables on Seasonal Activities
Clutches or litters Number of clutches or litters produced each year. Not limited
per year to successful clutches because there is no parental care in
most temperate species.
Days incubation Measured from laying of last egg to hatching. The duration of
incubation depends on the temperature of the substrate into
which eggs are laid.
Juvenile growth rate Usually reported as grams per day during a specified age (or
size) interval. May be reported instead as a series of weights
for juveniles of specified sizes if those are the only data
available.
Length at sexual maturity Length at which the first successful reproduction usually
occurs (see above). More commonly reported than weight or
age at sexual maturity.
1.5.4. Seasonal Activities
The meaning of most of the factors included under seasonal activities are selfevident.
Those requiring additional explanation are described in Sections 1.5.4.1 through
1.5.4.3. The column headers for this section of the table are shown in Table 1-9.
1-29
1.5.4.1. Birds
Mating/laying These two factors are combined because birds lay eggs within
a day or two of mating (they begin mating a day or two prior to
laying the first egg).
1.5.4.2. Mammals
Mating Although for most mammals the mating season corresponds to
conception and is followed immediately by gestation, some
species exhibit delayed implantation.
Parturition Birth of the pups (also known as whelping for canids).
1.5.4.3. Reptiles and Amphibians
Mating Because fertilization is external for many amphibians (i.e., most
toads and frogs and some salamanders), mating occurs at the
same time as egg-laying for these species. For reptiles,
fertilization is internal, and for some species, sperm may be
stored for months or years following mating.
Nesting Because many female reptiles can store sperm, nesting (i.e.,
egg-laying) often occurs weeks or months after mating.
1.5.5. Abbreviations Used in Tables
Age (life stage)
A adult (for all groups)
B both adults and juveniles/yearlings (for all groups)
C chick (for birds)
E eft (for newts)
F fledgling (for birds)
H hatchling (for birds, reptiles, and amphibians)
J juvenile (for all groups)
N nestling (for birds)
or
neonate (for mammals, water snakes)
P pup (for mammals)
T tadpole (for frogs)
Y yearling (for all groups)
1-30
Sex
B both sexes
F female
M male
Units
time: energy:
d day cal calorie
wk week kcal kilocalorie
yr year
mass: area:
g gram ha hectare
kg kilogram m square meter2
length: volume:
mm millimeter ml milliliter
cm centimeter l liter
m meter
km kilometer
temperature:
C degrees Centigrade
Other
NS not stated
1.6. LITERATURE SEARCH STRATEGY
The profiles in this Handbook are intended to provide a readily available
compendium of representative data for each selected species to assist in conducting
screening-level exposure assessments. They are not intended to provide complete
reviews of all available published and unpublished information or indepth biological
summaries. Moreover, the Handbook is not intended to replace field guides or natural
history or animal physiology texts. We have attempted to balance generalities, accuracy,
and coverage of each species relative to the available literature to meet our stated
purposes. We describe the process by which we identified literature for the Handbook
below.
1-31
The U.S. Fish and Wildlife Service (USFWS) Office of Information Transfer
conducted the primary literature search for species-specific information using their Wildlife
Review/Fisheries Review database. The database is compiled by USFWS personnel from a
review of over 1,130 publication sources (largely journals, but also USFWS publications)
from the United States and other countries, most dating back to 1971. The search was
conducted in May 1990 using common and scientific species names, but no further
restrictions on search terms were applied. All titles identified for each species were
reviewed to determine potential utility for the Handbook, and promising references were
reviewed in full. Recent review articles, handbooks, and natural history texts were used to
identify other relevant literature and literature from before 1971. Commercial databases
were not searched initially. Following peer review of the Handbook in 1991 and 1992, all
references submitted or identified by peer reviewers were evaluated, and additional
relevant citations were obtained for review. Limited (1970 forward) literature searches for
some species were conducted using commercial databases in 1992.
For information concerning physiology, allometric equations, energetics, and other
general topics, literature was identified on the basis of recent review articles or books in
the field suggested by experts in the field and by peer reviewers.
Because of resource limitations, we have included some values from secondary
citations. In these cases, our intent was to carefully record the original source and to
clearly indicate from which secondary source it was obtained. Users are encouraged to
obtain the primary sources to verify these values.
We used certain field guides consistently throughout each taxonomic category to
provide greater comparability of general species characteristics. The use of a specific field
guide does not constitute endorsement.
Because our literature search strategy may not have included all journals of interest
and did not consistently cover other sources of information (e.g., books, theses,
dissertations, state wildlife reports, conference proceedings), we would appreciate any
assistance that users might provide in identifying additional sources of information that
1-32
would help to fill data gaps or to improve the information in the Handbook. In particular,
Ph.D. dissertations and master's theses often contain relevant but unpublished
information.
1.7. REFERENCES
Peters, R.H. (1983) The ecological implications of body size. Cambridge, England:
Cambridge University Press.
U.S. Environmental Protection Agency. (1989a) Risk assessment guidance for Superfund:
volume II--environmental evaluation manual, interim final. Washington, DC: Office of
Solid Waste, Office of Emergency and Remedial Response; EPA report no.
EPA/540/1-89/001A.
U.S. Environmental Protection Agency. (1989b) Ecological assessment of hazardous waste
sites: a field and laboratory reference. Corvallis, OR: Environmental Research
Laboratory; EPA report no. EPA/600/3-89/013.
U.S. Environmental Protection Agency. (1989c) Exposure factors handbook. Washington,
DC: Office of Health and Environmental Assessment; EPA report no. EPA/600/8-
89/043.
U.S. Environmental Protection Agency. (1992) Evaluation of terrestrial indicators for use in
ecological assessments at hazardous waste sites. Washington, DC: Office of
Research and Development; EPA report no. EPA/600/R-92/183.